Prime mover for electric catapults



A118. 27, 1946- R. c. JONES ETAL 2,406,381

PRIME MOVER FOR ELECTRIC CATAPULIS Filed Aug. 31, 1943 INVENTORS /?(/e/61 Jb/Yes 0/70 Mao/1C9 l-T'Jozres.

ATTORNEY Patented Aug. 27, 1946 2,406,381 PRIME MOVER FOR ELECTRICCATAPULTS Rue! C. Jones, Pittsburgh,

Wilkinsburg, Pa., assi Electric Corporation, corporation of Pennsy andMaurice F. Jones,

gnors to Westinghouse East Pittsburgh, Pa., a

lvania Application August 31, 1943, Serial No. 500,641

The present invention relates to the control of linear motors and thepower plants therefor, in a manner suitable for energizing towing-carcatapults for launching aircraft. The general type of apparatus to whichthe present invention applies constitutes the subject-matter of thedescription and claims of an application of Frank B. Powers, Serial No.473,843, filed January 28, 1943, for Electric towing-car catapult foraircraft, assigned to the Westinghouse Electric & Manufacturing Company.

An object of the present invention is to provide means for controlling apower-generating unit in a manner to facilitate obtaining maximumpossible power-output from the prime-mover, particularly underconditions where the load is to be accelerated rapidly.

A further object of the invention is to provide a control which isactuated by the rate of change in the speed of the prime-mover, as wellas by the speed itself.

Another object of a power-plant which the invention is to provide can beoperated at substantially constant speed at full throttle of the englueor engines, the speed being held approximately constant at the speed ofthe maximum engine-output, the engine or engines being utilized to drivean electric generator or generators which, in turn, drive the catapultmotor.

A more specific object of the invention is to hold the engine-speedconstant, at approximately its maximum-output point, by means of varyingthe excitation of the electric generators which are driven by the engineor engines, so as to regulate the electrical power-output at such valueor values as may be necessary to keep the engine running at its speed ofmaximum performance.

A further object of the invention is to provide an overspeed relay, oran acceleration-relay, or both, for shorting out a portion of thefield-resistance of the generator or generators of the power plant, inresponse to a pro-selected speed or a pre-selected rate of accelerationof the engine, as the case may be. In like manner, we provide anunderspeed relay, or a decelerationrelay, or both, for introducing ablock of fieldresistance into the generator field-circuit in response toa slightly lower speed, or in response to a predetermined rate ofacceleration of the engine.

With the foregoing and other objects in View, the invention consists inthe systems, combinations, apparatus, parts, circuits, and methods,hereinafter described and claimed and illustrated in the accompanyingdrawing, the single figure 2 Claims. 290-17 grammatically represented,

of which is a simplified diagrammatic view of circuits and apparatusillustrating the invention in a preferred form of embodiment.

As diagrammatically illustrated in the drawing, an electric catapultinvolving the present invention includes a linear-motor towing-car, atrack therefor, and electrical supply-means and control-means therefor.The towing-car is diaat the bottom of the figure, by the three-phaseprimary windings WA, W13, WC of the linear-motor, the winding beingillustrated as a star-connected winding having a star-point O.

The track is diagrammatically represented as comprising two track-railsI and 2, two thirdrails 3 and i, and a linearly disposed secondarycore-member 5 carrying a squirrel-cage secondary-winding, which isrepresented by the numerals 6 and 1. A described and claimed in anapplication of Maurice F. Jones, Serial No. 506,197, filed October 14,1943, the track is preferably fabricated in a plurality of sections TIto T35, suitably joined together, any desired number of sections beingutilized, according to the desired length of run. A certain number oftrack sections (seven, as illustrated), at each end of the track, havehigh-resistance squirrel-cage windings, as indicated by the bent orfolded end-connections B in the drawing. The large intermediate group oftrack-sections, represented by the twenty-one sections T0 to T28 in thedrawing, have low-resistance squirrel-cage windings, as represented bythe low-resistance end-connections 1.

Three-phase electric power is supplied to the track, and thence to thecar-motor WA, WB, WC, by means of line-conductor Ll, L2, and L3, thespecific arrangement of which, to suitably reduce the reactance, whichmight otherwise be xcessively high, being the subject-matter of anapplication of Maurice F. Jones and Lee A. Kilgore, Serial No. 506,198,filed October 14, 1943. Two of the phases of'the power-supply areconnected to the third-rails 3 and 4, while the third phase, representedby the line-conductor L2, is connected. to the two track-rails I and 2,by means of connectors 8, there being a separate connection for eachsection of track.

Electrical power i supplied to the line-conductors Ll, L2, and L3, inthe one phase-sequence or the other, by means of two groups ofelectrically operated power-switches A, B, C and D, E, F. Thepower-switches A, B, and C energize the car-windings WA, WB, WC in thephase-sequence for operation toward the left, while the it E, and F arefor acceleration toward the right. The power-switche A, B, C, or D, E,F, supply power to the line-conductors LI, L2, L3 from a three-phase busTI, T2, and T3.

In the form of embodiment of the invention, as illustrated, three-phasepower is supplied to the bus TI, T2, and T3 by means of three generatcrsGI, G2, and G3, or other sources of threephase power which, in the formillustrated, are advantageously sources of somewhat poorvoltage-regulation, so that, when the motor-load is particularly heavy,the voltage drops somewhat. The generators GI, G2, and G3 aresynchronous generators having field-windings PW. Each generator isdriven by its own explosion-type gasoline engine or other prime-moverPMI, PMIZ, or PMEI, as the case may be, each having its own shaft. Thefield-windings FW of the three generators are excited from aneXciter-bus which is represented by the terminals E+ and E, theexciting-circuit being traceable from the E-lterminal, through threefield-resistances RI, R2, and R3, to a common field-winding terminal FIfrom which separate connections are made, through the respectivefield-windings FW, to the negative eXciter-bus E-. In normal operationof the gencraters, with the prime-movers operating, and thefield-windings excited, the three prime-mover shafts are electricallysynchronized by reason or the common bus-connection or the three-phasegenerator-terminals TI, T2, and T3.

The power-plant just described includes also three centrifugal switchesor other speed-responsive relays SI, S2, and S3, and anaccelerometerrelay AR. The first speed-responsive relay SI is designedto respond when the prime-mover speed is increased from the idling speedup to a speed which begins to approach the normal operating-speed, thisrelay responding to a speed, perhaps of 2250 R. P. M., or other desiredspeed. The second speed-responsive relay S2 is designed to pick upsensitively at a speed very slightly above the desired normaloperating-speed, and to drop out sensitively at a speed very slightlyherebelow, the normal operating speed being the speed at which theprime-movers deliver their maximum output, when operating at fullthrottle. This second speed-responsive relay S2 may be though of aspicking up at 2450 R. P. M., by way of example, and dropping out at 2425R. P. M. The third speed-responsive relay S3 is an overspeed devicewhich picks up at some overspeed, such as 2800 R. P. M.

The accelerometer-relay AR is designed to respond to a predeterminedrate of acceleration or deceleration of the prime-movers. It consists ofa central contact-arm 9, which is rotated with the shaft for engagingeither an acceleration-responsive contact IilA or adeceleration-responsive contact IIlD, when the shaft celerates at apredetermined rate, such as 50 revolutions per minute per second. Theaccelerometer-relay AR is provided with three slip-rings II for makingconnection to the central relayarm 9, and the two contact-points IilAand HID, respectively.

As described in an application of Ruel C. Jones and Maurice F. Jones,Serial No. 500,640, filed August 31, 1943, twenty-one electricallyenergized track-relays TR8 to TR28 are provided, one for each of thelow-resistance track-sections T8 to T28, these track-relays beingenergized by ourrent-transformers 8T in the individual tracksectionleads 8 which supply energy to the trackrails I and 2 of thecorresponding track-sections.

power-switches D,

accelerates or de- The design is preferably such that any track-relay Trwill be energized in response to the powercurrent which is fed into thetowing-car at about the time when the center of the towing-car is nearthe center of the corresponding track-section Tcc, or at otherpredetermined point in the travel of the car, responsive to the point,along the track, at which current is being fed into the car at themoment.

Cooperating with the twenty-one track-relays TRB to TR28 are twentyselector-switches which are diagrammatically illustrated at SE! to S28,these switches being preferably of the retainedcontact type, or any typeor kind whereby a predetermined one oi these switches may be selectedand closed by the operator, in order to pre-select the point in thetrack at which the towing-car will be deenergized, so as to pre-selectthe length of run, in accordance with the weight or the aircraft (notshown) to be launched, with due regard to the prevailing direction andvelocity of the wind at the time.

Preferably, the track-relays TRG to TR28 are or the latched type, orother retained-contact type, so that, when once actuated, each willremain in its actuated position until it has been reset, as by means ofa reset coil I2.

The control-equipment also includes three field-control relays FRI, FR2,and FRS for short ing out the respective field-resistances RI, R2, andR3. Further items of the control-equipment include an auxiliaryoverspeed-relay 83A, an interlock-relay IR, and a throttle-closer rclayTCR, all of which will be more specifically referred to in thesubsequent description of the operation.

The electrical control equipment for the catapult comprises twocontrol-drums DD and TD, which are shown at the top of the figure, a control-switch CS which is shown between them, and

a spotting-switch SS which is shown underneath the drum TD. Asindicated, the controlswitch has an On position and a Reset position.The drum DD is a direction-selecting drum having n Off position and twooperating positions marked Left and Right, corresponding to the desireddirection of aircraft-launching. The drum TD is a take-on drum which isillustrated as having an Off position, an Idling position, and aTake-off position. The drawing has been simplified by omitting the Testposition and contacts of the drum TD, for testing out the variouscircuits. The spotting-switch SS can be moved to either the left or theright, according to the direction of acceleration or movement desired tobe imparted to the car while it is being return to its starting point.This switch has first and second Left contacts I5 and I5, and first andsecond Right contacts I! and It, the first-position contact-points I5and Il being arcuate contacts which are engaged in the second position,as well as in the first position, of the movement of the switch-handle.

The operating-control connections may be traced from the control-switchCS. When this switch is in its normal or On position, a circuit iscompleted from the positive terminal of a suitable source of relayingenergy, indicated as a positive bus and a conductor 26, to a conductor2|, which is connected to a correspondingly numbered contact-point onthe drum DD.

It will first be assumed that the towing-car is at the leit-hand end ofthe track, at or near the track-section TI, and is to be moved to theright for the purpose of accelerating some aircraft (not shown), for thepurpose of launching the same. The direction-selecting drum DD is firstmoved to its ri ht-hand position, to pre-condition the control-circuitsfor a right-hand run, and the drum DD will be assumed to be in thisposition. At the drum DD, the conductor 2| is connected to a conductor22 which extends to a correspondingly numbered contact-point on thetake-oil" drum TD.

It will be assumed that the three prime-movers PM I, PM2, and PM3 areoperating at their idling speed, and that the three generator-fields FWare excited with a minimum excitation, with all three of thefield-resistances RI, R2, and R3 in the field-circuit.

When, now, the signal is given for take-off, the operator moves thetake-off drum TD to the Take-off position, which connects the conductor22 to the contact-points 23 and 31 of the take-oil drum TD. Theconductor 23, which is connected to the contact-point 23 of the drum TD,is connected to a correspondingly numbered contact-point of the drum DD,but no contact is made with this point, in the right-hand position ofthe drum DD. The conductor 23 also extends to a back-contact of the lasttrack-relay TRZB, this relay-contact being sufiiciently identified byreference to the relay-designation TREE. A relaying circuit is thereuponcompleted in series through the back-contacts of all twenty-one of thetrack-relays TRZS to TBS. As only certain illustrative track-relays havebeen shown, this relaying-circuit can be traced, from the conductor 23at the relay T328, through the conductors 25, and 29, and. the variousrelay-contacts, to a correspondingly numbered contact-point 29 on thedrum DD.

A pie-selected one of the se1ector-switches S9 to S23 also waspre-selected, prior to take-off, the usual interlocks being omitted forthe sake of clarity. For purposes of illustration, it will be presumedthat the selector-switch-Sm was closed. This makes abypassing-connection from the conductor 2'! of the track-relay TRzr,through the S3: contact to a conductor 3?}, which extends to acorrespondingly numbered contact-point on the drum DD, where aconnection is made to the conductor the drum being in its right-handposition. This bypassing-connection thus shortcircuits all of thetrack-relay contacts which are interposed between the conductor 29 andthe conductor 2?, so that the relaying circuit will not be broken,during the movement of the car, as subsequently described, until the carreaches the track-section Tm and energizes the track-relay TRzr, whichwill thereupon break the connection between the conductor 23 and theconductor 29.

The conductor continues, from the correspondingly numbered contact-pointof the drum DD to th first speed-responsive relay SI, which picks up at2250 R. P. M., or other speed which begins to approach the optimumrunning-speed oi the engine, and makes a contact with a conductor 33,which extends to a correspondingly numbered contact-point 33 on the drumDD. In its right-hand position, the drum DD connects the conductor 33 toa conductor 34, which extends down to the power-switches D, E, F toenergize the same, in series with back-contacts on the power-switches A,B, and C, the circuit being completed at the negative terminal at theoperating-coil of the relay F. In this manner, the power-switches D, E,and F are energized, closing their main contacts which energize theleads LI, L2, and L3 from the bus-terminals Tl, T3, and T2,respectively, thus energizing the carwinding WA, WB, WC in thephase-sequence suitable for driving the car toward the right. Thiscauses the car to start and to rapidly accelerate in its right-hand run,or the run from its starting point at the track-section Ti.

It will be noted that the conductor 29 was energized as soon as thetake-oil drum TD was moved to its Take-off position, and that itremained energized until the car reached the pie-selected track-sectionTm, as controlled by the selector switch Sr. As soon as this conductor29 was energized, upon the initial movement of the takeoff drum TD toits "Take-off position, another relaying circuit was made, as describedand claimed in an application of Ruel C'. Jones, Serial No. 500,638,filed August 31, 1943, through the back-contact of the 63A relay, to aconductor 35 which energizes the TCR relay, and also energizes threethrottle-closure magnets T03, 'ICZ, and TC! on the three prime-moversPMS, PMZ, and PMl. At the same time, a throttle signal-light LT isenergized from the conductor 35, so as to provide a signal, at thepower-plant (which is usually somewhat removed from thecontrol-station), that the take-oil moment has arrived.

The energization of the throttle-closer magnets TCI, T02, and T03 eitherautomatically opens the throttles wide (at a predetermined slow rate ofopening, commensurate with safety to the engines) or preferably they areutilized merely to stop holding the throttles in their closed or idlingpositions, so as to make it possible for the engineattendant to open therespective throttles as soon as the throttle signal-light LT comes on.At any event, gasoline, or other fuel, is supplied to the prime-moversat as rapid a rate as possible, until full-throttle conditions have beenreached, and the engines begin to rapidly accelerate from theiridling-speed, to their normal operating-speed.

It will be recalled that when the take-oil drum TD was first moved toits Take-off position, it also energized a contact-point 37 from theconductor From the contact-point 3?, a conductor Bl extends to theenergizing-coil of the interlocking relay IR, so as to cause it to pickup and close its make-contact.

It will be recalled that the contact-point 33 on the drum DD is the onewhich is connected to the power-switch conductor 34, in the right-handposition of said drum DD, so that the energization of the conductor 33applies tractive power to the towing-car for accelerating the car in thepreselected, right-hand direction, and the deenergizatio-n of theconductor 33 discontinues this pre-selected, right-hand energization ofthe towing-car, The conductor 33 also extends, through a back-contact ofthe first field-relay FRI, to a conductor 38, which is connected,through the IR relay-contact, to a conductor 39 which energizes theoperating coil of said first field-relay FRI. Thi causes said relay FR!to pick up and close a holding-contact which energizes the aforesaidconductor 38 from the conductor 37, this holdingcontact being madebefore contact is broken with the conductor 33. This first field-relaFBI is thus energized simultaneously with the application of power tothe towing-car, and it shorts out the field-resistance Rl which bringsup the fieldexcitation to perhaps two-thirds of normal, or other desiredvalue.

The conductor 38 also extends to the operating coil of the secondfield-relay FRZ and thence to conductor iii, which is connected to thenegative bus-terminal through a resistance R49. This causes the relayFRZ to pick up and short out the field-resistance R2, which brings thefield the conductor to the conductor 4! and ener up from two-thirdsof'normal t nearly normal field-strength, or other desired value.

In accordance with our present invention, the conductor 3'! also extendsto the second centrifugal switch S2, which connects said conductor 37 toa conductor M, when the prime-mover speed attains its value of maximumpower-output, which may be of the order of 245i) R. P, M. The conductorii energize the third field-relay PR3, which picks up and shorts out thefield-resistance R3, which ovcrexcites the generator-fields by some 40%or other desired value.

In accordance with our invention, the con ductor 38, in addition toenergizing the first and second field-relays FRl andFRZ, also extends tothe accelerometerqelay AR, and specificall to the movable contact-member8 thereof. When the prime movers are accelerating at at least apredetermined rate, such as 50 revolutions per minute per second,contact is made with the accelerometer-contact IQA, which is also joinedto the conductor 4! which energizes the third fieldrelay When theprime-mover speed is decelerating at a similar rate, contact is madewith the accelerometer contact ISD, which energizes a conductor 472.

The time-constants of the exciting circuits of the generators C l, G2,and G3 are such, however, that it takes the generators a certainmeasurable time to build up their excitations after the resistance inthe field-circuit has been decreased. In an illustrative example, thegenerators took about, one-fifth of a second to change their excitationhalf-way from a former value to a subsequent value, in response to anychange in the exciting-conditions, which compares with a timerequirement of between six and seven seconds for a OO-foot run of thetowing-car.

Before the energization of the power-switches D, E, and F, from theconductors 33 and 3 all three of the field relays FRl, PR2, and PR3 weredeencrgized, so that the field-excitation, and hence the voltage, of thegenerators were very low. Thus, the towing-car motor is started with arelatively low voltage applied thereto, and this voltage increasesrapidly and smoothly as the fieldexcitations of the generators build up,in accord ance with ieir time-constants. [it the same time, thegeneratowspeed is increasing fromthe value, such as 2250 R. P. M., whichclosed the first speed-switch Si, to the normal value of 2456 R. P. M.,because full throttle is being applied. to the e wines as fast as theycan safel take the gas 01 other fuel-oil, while the electrical output ofthe generators is low because of the slow building up of thegenerator-fields. In general, therefore, the prime-movers will beaccelerating at more than 50 revolutions per minute per second, so thatthe accelerometer relay AR will connect the field-relay FRB, so as to beincreasing the field-strength of the generators at a maximiun rate.

As described and claimed in the application of Ruel C. Jones, Serial No.500,638, the third, or overspeed, centrifugal switch S3 is utilized toenergize a conductor 43 from the positive relaybus and the conductor d3energizes the operating coil of the auxiliary overspeed-relay 53A. Thiscauses the auxiliary relay SSA to pick up, accomplishing two functions.It opens back-contact which disconnects the conductor from the conductor29, thus deenergizing the throttle-control magnets TC3, T02, and TC I.The energization of the auxiliary overspeed-relay 8 SSA also closes itsthree make-contacts, which ground the three ignition or magneto-leadsII, I2, and I3 of the three prime-movers PMI, PM2, and PM3, thusgrounding the primary-windings of the ignition or magneto-transformersITI, 1T2, and 1T3 of the engines.

The deenergization of the throttle-control magnets TCI, T02, and 'IC3may be caused to automatically partially close the throttles, but at aslow rate, taking one second, or other time, to close the throttles totheir idling setting, or the control may be left in the hands of theengineoperator in obedience to the signal conveyed by the extinction ofthe throttle signal-light LT which is extinguished at the same time thethrottle-closer magnets 'ICl, TC2, and TC3 are deenergised. Theautomatic closure of the throttles is preferred, at a time-ratecommensurate with engine-safety.

Since it is impossible, with safety, to close the throttles fast enoughto prevent overspeeding of the engines, it is desirable, as described,to shortcircuit, or otherwise deenergize, the engine-ignitions, whichinstantly interrupts the engine-outputs. At the same time, it isdesirable to reduce the throttle-setting so as to reduce the quantity ofunexploded gas in the engine-cylinders after the ignition ormagneto-circuit has been grounded.

The auxiliary overspeed-relay SBA is necessary, as it is not practicalto have the four contacts of this relay operated directly by thecentrifugal relay S3.

The throttle-control relay TCR has make-contacts which are adapted toconnect the conductors 6i and 42, the conductor 32 being connected tothe deceleration-contacts IEID of the acceleration-relay AR. Thus, ifthe engines or primemovers should be so overloaded that they aredecelerating at a rate of revolutions per second, or more, at a timewhen the engines are operating at full throttle, the accelerometer-relayAR will connect the conductor 33 to the condoctor 42, and thence,through the TCR contact, to the conductor 46, which short-circuits theoperating-coil of the second field-relay PR2, thus introducing thefield-resistance R2 and reducin the load on the engines, allowing theengines to speed up to normal speed again.

Whenever the engine-speed reaches 2450 R. P. .M., the secondspeed-switch S2 operates and energizes the third field-relay PR3, whichshort-circuits the field-resistance R3 and increases the electricaloutput of the generators, thus increasing the load on the engines andcausing the engine-speed to fall off slightly. When the speed falls to2425 R. P. M., the S2 centrifugal contact opens and deenergizes thefield-relay FR3, thus decreasing the generator-voltage and decreasingthe load on the engines, permitting the speed to increase again. Thusthe engine-speed, and hence the frequency of the generator-output, areheld substantially constant.

It will be recalled that the relay-conductor 31 was energized by thetake-ofi drum TD. As described and claimed in an application of Ruel C.Jones, Serial No. 500,639, filed August 31, 1943, another circuit fromthe conductor 31 extends to a make-contact of the first track-relay TR8,corresponding to the first track-sectionTS having a low-resistancesquirrel-cage winding 1. At an early part of the run of the towing-car,when it reaches the track-section T8, the track-relay TRB picks up, andconnects the conductor 44 to a conductor '45 which leads to acorrespondingly numbered contact-point on the drum DD, where thisconductor is connected to a conductor 46. The conductor 46 leads down tothe left-hand, or reversing, power-switches A, B, and 0, throughback-contacts of the right-hand, or ship-launching, power-switches D, E,and F.

Thus, at an early stage in the movement of the towing-car, a partialrelaying-circuit is set up, energizing the reversing power-switchconductor 45 from the positive relaying-bus starting with the conductor29 at the controlswitch CS, and extending through the contactpoint 24 ofthe take-off drum TD. The reversephase-sequence power-switches A, B, andC are not immediately energized, however, because the other threepower-switches D, E, and F had previously been energized in order tocause the car to move toward the right along the track.

The right-hand power-switches D, E, and F are deenergized, in general,in response to the selector-switch selection Sr, which pro-selects thelength of car-run. As soon as all three of the right-hand power-switchesD, E, and F are open, the previously partially energizedrelaying-circuit 5 comes into play, to instantly energize the threeleft-hand power-switches A, B, and C, so as to immediately apply powerto the car in the reverse phase-sequence, producing a force tending tomove the car toward the left.

When the forward or right-hand powerswitches D, and F were firstdeenergized, as a result of a pre-selected length of run, the conductor29 was deenergi ed, and this resulted in simultaneously deenergizing theconductor 35 at the back-contact of the auxiliary overspeed relay S-iA,simultaneously with the reversed energizetion of the car-motor WA, W3,W0. The deenerg zation of the conductor 35 deenergized thethrottle-control relay TCR, the throttle signallig t LT, and thethrottle-control magnets TCI, T02. and T03. As previously described inconnection with the operation of the overspeed-relay S3, thedeenergization of the throttle-control circuit 35 results in bringingabout the slow closure of the engine-throttles to the idling posit onsof the throttles, this closure being effected in a time which maybe ofthe order of one second or any other time dictated by conditions ofsafety to the engines.

Meanwhile, however. the car is stron ly d c lerating. because it isrunnin free of its towing load, and it has the full output of thegenerators Gi. G2, and G3 ano ied thereto in the reversephease-seouence. At the first portion. at least. of this deceleratin orbrakin eriod of the car, the engines are running at substantially fullthrottle, as described and c aimed. n t e ap plication of Ruel C. Jones,Serial No. 500.638.

During the one-tenth of a second, more or less. required to open theforward power-switches D, E, and and close the reverse powewswitches A,B. and C. the engines were operating at full throttle, without any load,hence the en.- gine-speed accelerated in, this brief period of time,sumciently to close the second speed-=responsive switch S2, or theaccelerometer-contact 89A, or both thereby energizing the thirdfieldrelay from the conductor 45. the first two field relays beingalready energized. from the conductor 38. Hence, as described andclaimed in the application of Ruel C. Jones, Serial No. 580,638, allthree field-relays FRi, and PR3 are energized, so that the car-braking iefiected at full generator-excitation, as well as at substantially thefull throttle of the engines, thus delivering the maximum availablepower to the towing-car in order to bring it to a stop as quickly aspossible.

As soon as the towing-car commences its return journey the operator atthe take-oh: drum TD should immediately move said drum to the Idleposition thereof. This does several things. It deenergizes the conductor3?, from which the reversing power-switch conductor and the field-relaysFRI, FRZ, and FRS, receive their energization. Hence it deenergizes thepowerswitches A, B, C, thus deenergizing the towingcar, and leaving itcoasting back towards its starting point. It also cleenergizes all threeof the field-relays, thus inserting the maximum resistace in thefield-circuits of the generators. The Idle drum-position energizes acontact-point ll of said drum TD, from the conductor 22, therebyenergizing the spotting-switch SS. It also connects two othercontact=-points 48 and A9 of the aforesaid drum TD to each other, thuselectrically connecting the correspondingly numbered conductors (i8 and49.

The car is now coasting back toward its starting-point, the engines arerunning at their idlingspeed, which is considerably lower than theiroperating-speed, and the generators are operating, not only at thisreduced speed, but also at the minimum available field-excitation, sothat the frequency and the voltage of the generators is very muchreduced, as described and claimed in the application of Ruel C. Jones,Serial No. 500,638.

To bring the car to a standstill, at the startingpoint, at the precisespot desired, the spottingswitch SS i utilized. The car is now moving tothe left toward the starting-point. To brake the car, thespotting-switch SS is moved to the first point to the right, connectingthe conductor 41 to the contact-point l1, and thence to the conductor 34which energizes the power-switches F, E, D. This applies a smallbraking-force to the car, and this braking-force is discontinued, at anymoment desired, by returning the spotting-switch to it central orneutral position. If the spotting-switch should be left too long onitsrighthand position, so that the car starts back again toward the right,the spotting-switch may be touched momentarily on its first left-handposition, engaging the contact-point l5, and thence connecting theconductor 41 to the conductor 46, which momentarily energizes thepower-switches A, B, and C. In case of emergency, the spottingswitch maybe moved to its second position, engaging either one of its contacts Itor IE, as the case may be, thus energizing the conductor 39 from theconductor Al, and energizing the first field-relay FRI, which cuts outthe field-resistance RI and provides increased power for controlling thetowing-car.

In the Idling position of the take-off drum TD, it has been noted thatthe conductor 48 is joined to the conductor ie. The conductor 48 isconnected to the Reset position of the controlswitch CS, so that, afterthe car has been brought, with the spotting-switch SS, to its desiredposition, at either end of the track, the controlswitch CS can be movedfrom its On position momentarily to its Reset position, thus momentarilyenergizing the conductor 58 from the conductor 20 and the positiverelaying-bus The conductor 3 3 is connected, in the Idling position ofthe take-off drum TD, to the conductor 49, which energizes all of thereset coils 12 in series, thereby resetting all of the track- 1 l.switches TRB to TRM. soon as these relays are reset (which takes but amoment), the'control-switch CS is returned to its On position, ready foranother launching.

In the preceding explanation, ithasbeen assumed that the car startedfrom track-section TI and operated toward the right. An importantfeature of the design, however, is that the car canbe operated fortake-off in either direction, with equal facility.

Thus, if the car should initially be standing at the other end of thetrack, or on the track-section T35,-so that it would be necessary totake off in a direction toward the left, the directionselecting drum DDwould be moved first to the Left position. The effect of thisdrum-setting would be as folows. The contact-point 2i would again beconnected to the contact-point 22. The contact-point 30 would beconnected to-the contact-point 23 rather than the contact-point 29.Thecontact-pointt l would be connected toa conductor 65, instead of theconductor 33, and the contact-point 46 would be connected to the coductor 33 instead of the conductor 45.

The changing of the conductor 33 from contact with the conductor .29 tocontact with the conductor 23 resultsin making the selectedselector-switch,such as S x+ 1), short-circuit the back-contacts of thetrack-relays between IE3: and the conductor 23, rather than between TRrand the conductor 29, so that the conductor 29 remains energized untilthe selected track-relay TRr is actuated, whereupon the conductor '29 isdeenergized, and the accelerating inovementof the towing-carisdiscontinued.

The effect of connecting the contact-point-46 tothe conductor 33 insteadof the conductor ill is to make the initial energization of thepowerswitches an energization of the switches A, B, and C for left-handoperation, under the controlof the conductor .33, thus setting up thecontrolcircuits for operation of the car in the left-hand direction.

The effect of connecting the conductor 34 to the conductor 525 insteadof the conductor 33 will be'seen from observing that the conductor 65 isconnected to a make-contact of the track-relay TRZB, which correspondsto the first track-section'T28 having a low-resistance squirrel-cagewinding 1 to be encountered by the car, in its travel toward the left.When the track relay T328 picks up, it thus closes its make-contact andconnects the conductor .65 to theconductor 31, thus setting up a partialenergizing-circuit, through the auxiliary timing-relay TA, which isready to energize the right-hand powerswitches D, E, F as soon as theleft-hand powerswitches A, B, and C drop out.

Since theoperation of the apparatus has been carefully described, in theprocess of the description, it is believed that no further summary ofthe operation is necessary. While a single form of embodiment of theinvention has been illustrated, it is to be understood that theinvention is not limited, in its broader aspects, to anylparticular formof embodiment, as many changes of addition, omission, and substitutionmay be made, without'departing from the essential features of theinvention. Itis desired, therefore, that the appended claim shall beaccorded the broadest construction consistent with their language.

W e claim as our invention:

1. An electric-motored device, and a power plant delivering a largeportion of its energy to saiddevice, said power plant comprising aretatable generator-means, prime-mover means for drivingsaidgeneratormeans, said o ne-mover means being of atypehaving a may mumout put at a particular speed, a variable field-excit ing means for thegenerator-means, accelerom" eter-means responsive to a predeterminedrate of acceleration or deceleration of the primernover means, andautomatic contro-l'means operative during a speed-changing period ofsaid electric-motored device toccntrol said flild-QX citing mean inresponse said accelerometermeans in such manneras to tend to'keepvtheacceleration or deceleration less than saidpred termined rate.

2. An electric-motored device, and a power plan-delivering alargeportion of its energy-to said device, said powereplant .a,rotatable generator-means, prime-mover meansfor driving saidgenerator-means, said prime-mover means having throttle-control meansand having a maximum output at a particular speed when operating at fullthrottle, a variable field-exciting means for the gcnratormreans,speedrespcnsive means responsive to a preselected spee which is close tosaid meximum-output speedof the prime-mover meas,accelerometermeansresponsive to a predeterrnined-raterof. acceleration or deceleration ofthe-prime-mover means iieldmontroloperative,-when energized,,to increasethe field-excitation-of said gen erator-mcans inresponseto eitheraresponse of said speederesponsive mean van accelerationresponseof saidaccelerorne and to de crease said fleld -excitation responseto either anon-response of said SPCWTE$DOI1S1VC means or a deceleration-responseof.saidaccelerometermeans, means for times one atingh (Lid primeh. movermeans substantially unloaded at are-- duced speed at a reducedthrottle-setting, with the electric-motored device in asubstantiallynon" energized condition, and controlnncans forat times energizing saide1ectric-motored device from said generator-means for a period of motor-acceleratioi said control-means also performing afunction which willresult infull throttle adjustment being given to said-primeemover means,and said control-means further. including means for energizing saidfield-control means.

RUEL C. JONES. MAURICE F. JONES.

